Propeller



E. MARTIN June 20, 1950 PROPELLER 3 Sheets-Sheet l Filed April 25, 1945 INVVENTOR Erle Mar-fin.

M {m I ATTORNEY.

E. MARTIN June 20, 1950 PROPELLER 3 Sheets-Sheet 2 Filed April 23, 1943 INVENTOR firfeyarzin M o M22 ATTORNEY June 20, 1950 E. MARTIN PROPELLER 3 Sheets-Sheet 3 Filed April 23, 1945 INVENTOR Er-ZeMarZz'zz BMW! Patented June 20, 1950 PROPELLER Erle Martin, West Hartford, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application April 23, 1943, Serial No. 484,229

' 8 Claims.

This invention relates to aeronautical propellers and particularly to a hollow all metal propeller blade having a central tubular supporting member extending longitudinally therein to which is permanently attached a covering member of sheet material conformed to airfoil shape and extending substantially throughout the entire active length of the blade.

A primary object of the invention is to provide a hollow all metal propeller of approved airfoil form, the outer surface of which is of stressed. skin type formed froma thin sheet of metal doubled longitudinally upon itself to form along its fold a major portion of the leading edge of the blade and having its opposite longitudinal edges brought together and welded to form the trailing edge of the blade, there being an inner tubular member welded or brazed to the outer member longitudinally along contacting portions of adjacent side surfaces, the inner tubular member before assembling being elongated and flattened progressively toward the tip portion, and preferably also having its wall thickness reduced gradually and uniformly from the shank to the tip portion of the blade.

Another important object of the invention is to provide a blade comprising an inner tubular member enclosed within an outer airfoil member or cuff, the tubular member forming the principal structural or stress sustaining member and being the sole connection between the airfoil member and the propeller hub; the outer member being secured to the tubular member as by brazing, soldering or otherwise along their adjacent surfaces throughout their length and at widely spaced portions laterally of the blade, thereby adding stiffness to the blade; both longitudinally and transversely and the outer member being conformed to an aerodynamically efficient shape throughout its length preferably after assembling.

A still further object of importance is that a practical and efficient light weight all metal hol low blade may be produced having its leading edge extending in a straight line in space for drawings which illustrate what are now considered to be preferred embodiments of the invention.

Fig. 1 is a longitudinal View in plan-form of a propeller blade made in accordance with the present invention, a portion being broken away to more clearly show its construction.

Fig. 2 is a fragmentary view of a slightly modified form of the blade showing the tip portion thereof in plan-form upon an enlarged scale compared toFig. 1.

Figs. 3, 4, 5, 6, '7 and 8 are cross sectional views taken on the planes of lines 3-3, 4-4, 5-5, 66, and 8-8 of Fig. 1.

Figs. 9, 10, and 11 are cross sectional views taken on the planes of lines 9-9, Ill-Ill, and

11-41 of Fig. 2.

Fig. 12 is a longitudinal plan form view similar to Fig. 1 and showing a further modified form of the invention, and

Figs. 13, 14, 15, 16, 17 and 18 are cross sectional views taken on the planes of lines l3l3, l4-l4, 15-45, I6-I6, I'|--I| and l8l8 of Fig. 12.

In its preferred forms the invention may include the following parts: First, a central supporting tubular member having before being flattened a bore of gradually reduced diameter toward its tip and having its outer diameter and its wall thickness gradually decreased progressively from shank to tip,'there being at the shank end of the tubular member means for attaching the blade to a hub; second, an airfoil shaped outer member 12 made from a metal sheet bent centrally and longitudinally upon itself and having its opposite longitudinal edges brought togather and welded or brazed from end to end; and third, seams formed by brazing, welding or soldering together the airfoil member and the tubular member along their adjacent surfaces on opposite sides of the blade substantially throughout their length.

Referring more in detail to the embodiment of the invention shown in the drawings, and first to the embodiment shown in Fig. 1, tubular member ID has a shank which is provided with grooves l l for connection to a propeller hub. In the finished blade, member H3 is gradually elongated and flattened toward the tip, and has its wall thickness progressively decreased toward the tip, the successive forms of this member at different distances from the shank being indicated by Figs. 3 to 6 inclusive in transverse sections. To limit the transverse dimensions of the tubular member due to this member being flattened, the member is materially elongated throughout its length prior to the flattening operation.

The outer member I2 is formed from a sheet of material of uniform thickness such as steel folded or bent, as shown more clearly in Fig. 3, substantially longitudinally and centrally to form a large portion of the leading edge I3 of the blade. The opposite longitudinal edges are trimmed substantially as indicated in Figs. 1 and 2 and are welded, brazed or otherwise permanently secured together along their entire length to form the trailing edge I4 of the blade. The leading edge I3 due to the sheet being folded or bent will be straight in space substantially throughout its length andpreferably is disposed parallel to the axis of the inner or tubular member Ill. At the tip the outer member I2 is rounded to any desired extent and the seam joining the edges of the sheet along the trailing edge I4 of the blade is carried around the tip and extends for a, short distance toward the shank along the leading edge I3.

The outer member I2 is conformed to its final airfoil shape by any preferred shaping operations so that member I2 forms an elongated airfoil cuff: for the blade extending from the shank to the tip and at the tip completely encloses the outer end of member ID. These two members IIiand; I2 are soldered, brazedor otherwise united permanently to each other from the shank to the tip along their adjacent or contacting surfaces. The method of manufacture of the two principal blade members and the method employed for their assembly is covered in a separateapplication Serial No. 484,254; filed April 23; 1943 by Glen T. Lampton.

Fig. 1 shows the tip end of the tubular member H) cut to form a central extended point flattened as indicated in the sectional views by bringing opposite surfaces into contact. The opposite fiattened surfaces of the tubular member are welded, brazed or. otherwise secured along their entire ac tive. length to the internal surfaces of airfoil member I2. Member Ill, however, as shown more clearly in Fig. 2, maybe extended directly to the tip so that the tip portion would consist of four sheets-ofmaterial-A. e. the camber face of the sheet I2, the flattened walls of the tubular member or core IQ, and the face side of the sheet I2. Alsoas shown in Fig. 2, the tip of the tubular member ID along its leading edge, may be substantially straight directly up to the tip of the outer'member I2 and have its trailing edge I4 trimmed as shown and welded or brazed together by any suitable means.

In the embodiment shown in Fig. 12, et seq., the inner or tubular member I5 is generally similar to those shown in Figs. 1 and 2 at its shank and intermediate portions but at its tip is different in that this end is symmetrical relative to the longitudinal axis of the blade and has a long tapered tip end portion I6 notched centrally as shown at ll. By means of this notch II, the tip of the tubular member I5 may be centered longitudinally of the blade by a small rivet I8 extending through opposite walls of the outer members I9. The trailing edge of the airfoil member I9 may have the opposite edges of the sheet from which it is formed brought together and brazed, preferably by a copper brazing operation. In this form of the invention the members I5 and I9 are united preferably by soldering, the solder employed being employed at a lower temperature than the copper used in brazing the trailing edge of vthemember I9 so that this edge will not be aifected. The width of the flattened tubular member I5 is such that the soldered joints along contacting surfaces of the tubular member I5 and airfoil member I9 are disposed a material distance apart laterally of the transverse dimension of the central longitudinal portion of the blade and serves to materially increase the stiffness of the blade transversely andlongitudinally.

The lateral edges of the contacting surfaces of the tubular and cover members on opposite sides of the blade are disposed a material distance apart, and a substantial distance on either side of the axis of the blade. The soldering or brazing material along these edges forms fillets as indicated in Figs. 13 to 18 and thus forms an extremely strong seam. These seams are laterally spaced apart transversely of the blade and thus greatly increase the longitudinal and transverse stiffness of the blade. Also, the overhanging lateral portions of the airfoil member I9 beyond the limits of the flattened tubular member are relatively short and in the active portions of the blade do not exceed one-third of the total width of the blade. The outer or airfoil member I9-in the embodiment shown in Figs, 12 etseq., may be similar to those shown in the preceding figures. Asindicated, the sheet from which this member is made is folded longitudinally upon itself and forms a straight leading edge for a substantial portion of its length. The trailing edge is formed by a welded or brazed seam whichis extended around the tip end to the point/indicated at 2.0.

In all the embodiments of the invention, the tubular members Ill and I5 may be axiallyelongated throughout their length and have their wall: thickness reduced toward the tip prior to their flattening operation. In this way the transverse dimensions of the tubular member. are materially reduced at the various progressively flattened sections of this member.

In operation, member III in all embodiments of the invention transmits all forces between the hub and airfoil member with the airfoil or outer member, due to its being united to the tubular memher as described above, adding longitudinal and lateral stiffness to the blade. The airfoil member extends substantially the entire active length of the blade, and'at its hub end may preferably be closed by plate It closely fitting about the tubular member Ill. I

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as defined by the following claims;

I claim:

1. A propeller blade comprising in combination, a sheet-metal, airfoil-forming elongated tubular shellclosed at one end and open at the other, a supporting metal tubular core extending lengthwise within said tubular shell and projecting from the open end of said tubular shell, said tubular core having a wall thickness greater than the thickness of said sheet metal andhaving its major transverse dimensions substantially parallel to, but substantially smaller than, the chord of said tubular shell but otherwise, conformed tov the chordwise shape of, and snugly fitting, over a substantial chordwise extent, the interior surface of said tubular shell, a hubconnection on the projecting end of said core, said tubular shell being held on and connected to said tubular core substantially. solely by a fusedmetal joint of a metal different from that of. the shell orycoreandconnecting substantially the entire snugly fitting surfaces.

2. A propeller blade comprising in combination a sheet metal airfoil-forming elongated tubular shell closed at one end and open at the other and having a lift-producing airfoil shape at the open end, a supporting metal tubular core extending lengthwise within said tubular shell and projecting from the open end of said tubular shell, said tubular core having a wall thickness greater than the thickness of said sheet metal and having its major transverse dimensions substantially parallel to but substantially smaller, thoughout the length of said core, than the interior chord of said shell but otherwise conformed to the chordwise shape of and snugly fitting, over a substantial chordwise extent, the interior surface of said shell, a hub connection on the projecting end of said core, said tubular shell being held on and connected to said tubular core substantially entirely by a fused metal joint of a metal different from that of the shell or core and connecting substantially the entire snugly fitting surfaces.

3. A propeller blade having an airfoil portion including a camber side and a face side and comprising in combination, a central tubular member having opposite sides corresponding to said blade sides progressively flattened toward the tip end of the blade and having hub connecting means at its shank end, said opposite sides conforming to the chordwise shape of, but separated a smaller distance than, the sides of said blade and having a chordwise dimension substantially smaller than said blade, and a covering member of sheet material doubled longitudinally upon itself and forming the leading edge of the blade at its fold and conformed to an airfoil shape comprising substantially the entire airfoil portion of said blade, said covering member having its longitudinal edges juxtaposed and secured together to form the trailing edge of said blade, said tubular member and covering member being telescopically arranged so that their corresponding sides provide chordwise extending adjacent surfaces said corresponding sides being soldered together substantially throughout said adjacent surfaces on opposite sides of said blade.

4. A propeller blade comprising in combination, a sheet metal airfoil-forming elongated tubular shell closed at one end and open at the other, a supporting metal core extending lengthwise within said tubular shell and projecting from the open end of said tubular shell, said core having its major transverse dimensions substantially parallel to, but substantially smaller than, the chord of said tubular shell but otherwise conformed to the chordwise shape of, and snugly fitting, over a substantial chordwise extent, the interior surface of said tubular shell, a hub connection on the projecting end of said core, said tubular shell being held on and connected to said core substantially solely by a fused metal joint of a metal different from that of the shell or core and connecting substantially the entire snugly fitting surfaces.

5. A propeller blade comprising in combination, a sheet metal airfoil-forming elongated tubular shell closed at one end and open at the other, a supporting metal tubular core extending lengthwise within said tubular shell and projecting from the open end of said tubular shell, said tubular core having its major transverse dimensions substantially parallel to, but substantially smaller than, the chord of said tubular shell but otherwise conformed to the chordwise shape of, and snugly fitting, over a substantial chordwise extent, the interior surface of said tubular shell, a hub connection on the projecting end of said core, said tubular shell being held on and connected to said tubular core substantially solely by a fused metal joint of a metal different from that of the shell or core and connecting substantially the entire snugly fitting surfaces.

6. A propeller blade as described in 3 in which the central tubular member has a wall thickness at the shank end of the blade greater than the thickness of said sheet material.

7. A propeller blade as defined in 6 in which the central tubular member and the covering member are both steel members.

8. A propeller blade as claimed in 3 in which the central tubular member and covering member are both metal members.

ERLE MARTIN.

REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 1,454,977 Middleton May 15, 1923 1,789,240 Leitner et al Jan. 13, 1931. 1,817,556 Hamilton Aug. 4, 1931 2,081,645 Squires May 25, 1937 2,231,888 Couch Feb. 18, 1941 2,262,163 Brauchler Nov. 11, 1941 2,272,439 Stanley Feb. 10, 1942 2,276,262 Caldwell et a1 Mar. 10, 1942 2,280,337 McKee Apr. 21, 1942 FORElGN PATENTS Number Country Date 221,906 Great Britain Sept. 25, 1924 226,301 Great Britain Dec. 24, 1924 231,919 Great Britain Apr. 7, 1925 433,122 Germany Aug. 23, 1906 546,176 Great Britain July 1, 1942 560,706 France July 17, 1923 700,360 Germany Dec. 18, 1940 

